Finding the Sum of Angles in a Triangle - JSS1 Mathematics Lesson Note

Regardless of the type of triangle, the sum of the interior angles is always 180∘.

Explanation with Examples:

Example 1: Equilateral Triangle

Triangle ABC is equilateral where all angles are 60∘.

Calculation: 60∘+60∘+60∘=180∘

Example 2: Isosceles Triangle

Triangle XYZ is isosceles with angles 50∘, 50∘, and 80∘.

Calculation: 50∘+50∘+80∘=180∘

Example 3: Scalene Triangle

Triangle PQR is scalene with angles 30∘, 60∘, and 90∘.

Calculation: 30∘+60∘+90∘=180∘.